My boss, and his manager, as well as several other people at our organization, have this same problem. A meeting invite is sent out to upper management, they click on "Accept" and the invitation e-mail then moves itself to the trash folder, marked as "Unread." They have to accept again in the trash to actually get the invitation posted to their calendar.
Obviously from reading a bit, LOTS of users of Office 2016 using Exchange have this problem. Please put your best minds on this ASAP.
Creating a new profile did not change anything.
We're running Windows 10 Pro, 64-bit, Office 2016 Home & Business. Our accounts are Exchange-based.